This invention relates to a chlorella-culturing apparatus capable of efficiently culturing chlorella. The customary industrial process of culturing chlorella was to charge chlorella and culturing liquid in a shallow circular water tank, stir the mixed mass while introducing carbon dioxide gas thereinto, and apply a required amount of light on the chlorella floating on the chlorella-culturing liquid. With the conventional industrial chlorella-culturing device, a stirring mechanism was fixed to the lower part of a rotatable arm body to rotate therewith for stirring. Though stirring streams were forcefully generated by the stirring blades in the chlorella-culturing tank, bacilli contained in the chlorella-culturing liquid and chlorella itself tended to precipitate and deposit on the bottom board and inner side walls of the chlorella-culturing tank, because the tank charge was left intact for a long time. Obviously, such deposition contaminated cultrued chlorella and restricted its growth in the pure form. Before, therefore, the chlorella-culturing tank was again charged with a fresh batch of chlorella mixed with a culturing liquid, it was necessary to remove deposits produced in the preceding culturing step from the culturing tank. However, the known chlorella-culturing apparatus was not provided with means for automatically scarping off such deposits to clean the interior of the chlorella-culturing tank. Consequently an operator manually took off deposits from the culturing tank by means of, for example, a brush. As naturally expected, the culturing tank had to be emptied, before the deposits could be manually removed. Accordingly, the customary chlorella-culturing apparatus failed to culture chlorella continuously, presenting difficulties in the efficient growth of chlorella.
Further with the prior art chlorella-culturing apparatus, the bottom board of the chlorella-culturing tank was inclined to cause the liquid therein gravitationally to flow to the tank outlet. Moreover, cultured chlorella was discharged together with a culturing liquid by a stirring mechanism mounted at prescribed position on the rotatable arm body. This arrangement consumed a great deal of time in removing the cultured chlorella, presenting difficulties in carrying out in quick and efficient exchange of a treated mixture of chlorella and culturing liquid for a fresh one.
This invention has been accomplished in view of the above-mentioned circumstances and is intended to provide an improved chlorella-culturing tank whose interior is kept clean for the efficient growth of chlorella.